This invention relates to an atmospheric deaerator unit for use in a boiler feedwater system for eliminating non-condensible gases from the boiler feedwater. Non-condensible gases are principally carried into the feedwater system by the addition of makeup water to compensate for losses during the steam cycle. Additionally, gases can be generated in the steam circuit, such as carbon dioxide, which is generated from carbonate salts reacting with metallic components in the steam circuit.
The atmospheric deaerator of this invention is of the type described in my prior U.S. Pat. No. 4,698,076 issued Oct. 6, 1987, entitled ATMOSPHERIC DEAERATOR UNIT, in my U.S. Pat. No. 3,487,611 issued Jan. 6, 1970, entitled SPRAY-FLOW DEAERATOR, and in particular, in my U.S. Pat. No. 4,874,406 issued Oct. 17, 1989, entitled JET SPRAY ATMOSPHERIC DEAERATOR.
Generally, deaerators are rated as either 0.03 cc/liter or 0.005 cc/liter deaerators. The latter being the most effective in removing dissolved gases. In general, to achieve a reduction of dissolved air and gases to 0.005 cc/liter, the deaerator must operate in a pressurized circuit. While the referenced patents entitled ATMOSPHERIC DEAERATOR UNIT, and JET SPRAY ATMOSPHERIC DEAERATOR, disclose two arrangements for achieving a high performance deaerator at atmospheric pressure, the deaerator of this invention provides an alternate solution for the problem of obtaining a high performance deaerator that is vented to atmosphere. Atmospheric deaerators are preferred for their safety features an their low cost in maintaining vessels at low temperatures and pressures.
The deaerator unit of the present invention is constructed with a divided vessel similar to the JET SPRAY ATMOSPHERIC DEAERATOR of U.S. Pat. No. 4,874,406 in which one side is steam pressurized to one to five psi. This small pressure differential allows for internal deaeration circuits that substantially reduce the venting of any steam and include simple temperature or pressure controls to maintain relatively constant temperature in the boiler feed water.